Ducted Systems, Static Pressure Settings...

[Kad]

Hello guys, according to your experience, on a "standard" ducted air con system, do you get better results setting the evaporator unit to high static pressure or low static pressure?

I'm asking this cause i've a weird situation here, i've a ducted system with quite a few meters of ducts, usually i would set the unit to high static pressure, funny thing here is that the unit seems to perform better when set for low static pressure.

KAd.

[The Viking]

Such a simple question yet so many variables...

The static pressure of the ductwork should be calculated at the design stage of the job and measured at commissioning.
The system should then be set up to operate with the measured resistance of the ductwork, unless you got one of Samsung's latest ducted units as they self adjust according to the static pressure.

What will work "best" in you situation is impossible to say, not least because "a few meters" of ductwork might equal 500pa or 5pa... It is all down to air volumes and areas.
Another variable is the grilles and their location, do they work best with a gale or a trickle coming out of them?

[frank]

Setting the unit for HIGH static or LOW static will result in the fan running faster or slower.

If you have the system running with the fan on High but with a low static resistance then the air volume and velocity will be increased and the dwell time through the evaporator will be short, giving a smaller dt (t1 - t2).

the unit seems to perform better when set for low static pressure.

With the fan running slower, the dwell time through the evaporator is longer, giving a bigger dt. If the dt is more than 8 -10K then your fan is running too slow for the amount of ductwork attached to it.